Software Quality Assurance

Unit IV

Software Quality

Software Quality is defined as:Conformance to

Explicitly stated functional and performance requirements,

Explicitly documented development standards, and

Implicit characteristics that are expected of all professionally developed software"

Software Quality

This definition emphasizes three points: Software requirements are the foundation

from which quality is measured; lack of conformance to requirements is lack of quality

Specified standards define a set of development criteria that guide the manner in which software is engineered; if the criteria are not followed, lack of quality will almost surely result

A set of implicit requirements often goes unmentioned; if software fails to meet implicit requirements, software quality is suspect

Software Quality Factors

Quality of a software product is associated with the following factors: Portability: a software product is said to be

portable if ▪ It can be easily made to work with different

hardware and operating system environments.▪ It can easily interface with external hardware

devices and software products. Usability: a software has good usability if:▪ Different categories of users (both expert and

novice) can easily invoke the functions of the product.

Software Quality

Reusability: a software has good reusability if ▪ Different modules of the software can easily be

reused to develop new products. Correctness: a software product is correct if:▪ Different requirements as specified in the SRS

document have been correctly implemented. Maintainability: a software product is

maintainable if:▪ Errors can be easily corrected as and when they

show up.▪ New functions can be easily added to the product,

and▪ The abilities of the product can be easily modified.

Responsibility of Software Quality

Software quality is not the sole responsibility of the programmer It extends to software engineers, project

managers, customers, salespeople, and the SQA group

Software engineers apply solid technical methods and measures, conduct formal technical reviews, and perform well-planned software testing.

The SQA Group

Serves as the customer's in-house representative.

Assists the software team in achieving a high-quality product.

Views the software from the customer's point of view Does the software adequately meet quality

factors? Has software development been conducted

according to pre-established standards? Have technical disciplines properly performed

their roles as part of the SQA activity? Performs a set of activities that address

quality assurance planning, record keeping, analysis, and reporting.

SQA Activities Prepare an SQA plan for a project Participate in the development of the project's

software process description Review software engineering activities to verify

compliance with the defined software process. Audit designated software work products to verify

compliance with those defined as part of the software process

Ensure that deviations in software work and work products are documented and handled according to a documented procedure

Record any noncompliance and reports to senior management

Coordinate the control and management of change

Helps to collect and analyze software metrics

Software Reviews

Purpose of Software Review

Serve as a filter for the software process Are applied at various points during the

software process Uncover errors that can then be removed Purify the software analysis, design, coding,

and testing activities Catch large classes of errors that escape

the originator more than other practitioners.

Purpose of Software Review

Include the formal technical review (also called a walkthrough or inspection) Acts as the most effective SQA filter

Conducted by software engineers for software engineers

Effectively uncovers errors and improves software quality

Has been shown to be up to 75% effective in uncovering design flaws (which constitute 50-65% of all errors in software)

Require the software engineers to expend time and effort, and the organization to cover the costs

Formal Technical Review or Walkthrough

Objectives To uncover errors in function, logic, or

implementation for any representation of the software

To verify that the software under review meets its requirements

To ensure that the software has been represented according to predefined standards

To achieve software that is developed in a uniform manner

To make projects more manageable

Formal Technical Review or Walkthrough Serves as a training ground for junior software

engineers to observe different approaches to software analysis, design, and construction

Promotes backup and continuity because a number of people become familiar with other parts of the software

May sometimes be a sample-driven review Project managers must quantify those work

products that are the primary targets for formal technical reviews

The sample of products that are reviewed must be representative of the products as a whole

SQA Plan: Purpose and Layout Provides a road map for instituting

software quality assurance in an organization

Developed by the SQA group to serve as a template for SQA activities that are instituted for each software project in an organization

SQA Plan: Purpose and Layout Structured as follows:

The purpose and scope of the plan A description of all software engineering work

products that fall within the scope of SQA All applicable standards and practices that are

applied during the software process SQA actions and tasks (including reviews and

audits) and their placement throughout the software process

The tools and methods that support SQA actions and tasks

Methods for assembling, safeguarding, and maintaining all SQA-related records

Organizational roles and responsibilities relative to product quality